Microstructure and mechanical properties of RPC containing PP fibres at elevated temperatures

This paper illustrates the effect of temperature on the microstructure and mechanical properties of reactive powder concrete (RPC) containing polypropylene (PP) fibres. Thermal conductivity, thermogravimetry, differential scanning calorimetry and mercury intrusion porosity measurements were taken and compressive and tensile strength tests were performed over a temperature range 20-800°C. The PP fibre content, specimen dimensions and explosive spalling were investigated as part of this study, and the various decomposition phases and microstructure were identified using X-ray diffraction and scanning electron microscopy. The experimental results indicated that the compressive and tensile strengths of RPC with PP fibres decreased as temperature increased. RPC containing PP fibres displayed better mechanical properties than normal-strength concrete or high-strength concrete. The addition of PP fibres at a dosage of 2.73 kg/m³ could prevent the explosive spalling of RPC and significantly increase its compressive and tensile strengths at elevated temperatures. Supplementary pores and small channels were created in the RPC due to the melting of PP fibres.